Not very often. I know on my VW Passat they want it checked at 120,000 miles. A lot of VW TDI's are going well past the 120,000 miles. Tractors should go about 4,000 hours or so. Most tractor manufacturers use them. I think Mahindra right now is the only one that does not use it. They use a Diesel Oxidation Catalyst (DOC). Massey uses DOC on a lot, but I think there smaller ones still use DPF. Kubota I think is starting to switch to DOC. Branson offers some with DOC.How often do these need to be cleaned or replaced? What companies offer tractors with them?
Mahindra is having a EGR problem with a lot of tractors right now. Both systems have positives and negatives.